Lung Cancer: Radiotherapy and Chemotherapy

Lung cancer is a common and serious type of cancer that is diagnosed in around 44,500 people in the UK every year. Lung cancer is cancer that originates in the trachea (windpipe), the bronchus (the main airway) or the tissue of the lung.

The treatment for lung cancer depends on the type, size and location of the cancer. The treatment for non-small cell lung cancer is different to that used to treat small cell lung cancer. Small cell lung cancer is generally treated with chemotherapy, because it has usually spread beyond the lung by time it is diagnosed and therefore cannot be treated by removing a part or all of the lung. People with small cell lung cancer may also be treated with radiotherapy.

Non-small cell lung cancer may be treated with surgery, chemotherapy, radiotherapy or a combination of these, depending on the stage of the cancer at diagnosis.

Radiotherapy

Depending on the stage and type of cancer, radiotherapy may be used:

• As an added measure after surgery to destroy any cancer cells that may remain and lower the risk of the cancer recurring.
• Prior to surgery in order to shrink the cancer and make surgery safer and easier.
• As the main treatment for individuals where the cancer is only present in the chest but cannot be surgically removed.
• In cases where people have other health problems that mean surgery is prohibited.
• To treat recurring cancer.
• As a palliative treatment, to decrease pain and improve quality of life.

Some of the main types of radiotherapy are described below.

Stereotactic Body Radiotherapy (SBRT), a form of external radiotherapy where intense doses of radiation are precisely delivered to affected tissue. This procedure minimizes the amount of radiation that reaches nearby healthy tissue and reduces side effects. An X-ray or CAT scan may be used to locate the exact location that needs to be targeted by the therapy.

Intensity-modulated radiotherapy (IMRT), a computer guided technique that is used to precisely target cancer cells. This also reduces the amount of radiation delivered to normal, healthy tissue and reduces side effects. An X-ray or CAT scan may be used to locate the exact location that needs to be targeted by the therapy.

Brachytherapy is internal radiation therapy. Tiny radioactive seeds are placed close to the site of cancer. Some patients may receive a particular type of brachytherapy called endobronchial brachytherapy, where high doses of radiation are delivered to the airways and exposure to surrounding normal tissue is minimized.

Chemotherapy

Chemotherapy is an important therapy in small cell lung cancer that uses drugs to attack cancer cells. This disrupts the cancer’s growth and small cell lung cancer often responds well to this form of therapy.

Cancerous cells divide in an abnormal manner that is no longer controlled, as it is in healthy cells. When healthy cell comes into contact with other similar cells, they stop dividing, a mechanism referred to as contact inhibition.

Cancerous cells, on the other had, lose this ability and cell division is no longer limited. Whether cells are cancerous or healthy, this process of cell division occurs through the cell cycle, which begins with the resting phase and moves through active growing phases and then to division or mitosis.

The success of chemotherapy at destroying cancer cells depends on how effective it is at halting cell division. The drugs usually work by damaging the DNA or RNA that instruct a cell to copy itself in division. Cells that cannot divide, then die. The faster cells are dividing, the more effective chemotherapy is likely to be and lead to shrinkage of the tumor.

Chemotherapy may be delivered intravenously or orally, using tablets. It may be given in cycles, with treatment being received for a period of a few days, which is then followed by a rest period. Chemotherapy drugs that only affect cells when they are dividing are referred to as cell-cycle specific and drugs that affect cells while they are in the rest phase are referred to as cell-cycle non-specific. Chemotherapy is therefore scheduled based on the type of cells, their division rate and the time when a drug is likely to be effective, which is why this therapy is usually delivered in cycles.

There are many different chemotherapy drugs and drug combinations that may be used to treat patients, but most commonly, cisplatin or carboplatin is used, often in combination with a therapy called etoposide.